Unprotected first intercourse and subsequent risky sexual behavior

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A study has found that women who did not use contraception during their first sexual intercourse have more subsequent sexual partners, induced abortions, and sexually transmitted infections (STIs), compared to  women who used condoms. 

The study in Contraception was based on questionnaire data collected in 2011 and 2012 from an eligible and responsive random sample of 45,361 women aged 18 to 45 residing in Denmark, Norway, and Sweden.

Among the participants, 58.3% used a condom during first sexual intercourse, 11.2% used oral contraception (OC), 7.3% used both OC and condom, 4.2% had intercourse during a safe period or used withdrawal, and 1.0% took an emergency contraceptive pill (ECP), whereas 18% of the women used no contraception at all.

ECP users were generally younger (median age 23) when filling out the questionnaire compared to women who used other contraceptive methods or no contraception at first sexual intercourse (median age range 30 to 35).

In addition, a higher proportion of contraceptive nonusers (37.0%) and ECP users (38.9%) had a low education level (high school or less) than women using the other contraceptive methods (range 26.6% to 32.1%).

A higher proportion of nonusers also had their first sexual intercourse before age 15 (17.0%) than women who used some form of contraception (range 6.0% to 12.8%).

Women who did not use contraception during first sexual intercourse were more likely than condom users to have 11 or more lifetime partners (OR=1.34; 95% CI: 1.27-1.42), induced abortions (HR=1.62; 95% CI: 1.53 – 1.71) and STIs (HR=1.15; 95% CI: 1.10 – 1.20).

ECP users were also more likely than condom users to have at least 11 sexual partners (OR=1.764; 95% CI: 1.40 – 2.22), induced abortions (HR=1.44; 95% CI: 1.11 – 1.86) and STIs (HR=1.84; 95% CI: 1.56 – 2.16).

A similar pattern was seen for women who had intercourse during safe periods or used withdrawal.

These associations also did not change among women who first had sexual intercourse starting in 2001 (n=14,445), when ECPs became available without prescription.

The authors’ previous studies validate the current findings that women tend to retain the same form of contraception throughout their life; for example, women who do not use contraception at first sexual intercourse are more likely to never use a condom, and women who use a condom during first sexual intercourse are more likely to continue using a condom.

Other previous studies have also shown that contraceptive nonuse is linked to induced abortions and STIs.

Studies have also concluded that women with multiple lifetime partners are less likely to use contraception and more likely to acquire STIs.

However, the investigators of the current study acknowledge that the mechanisms responsible for the associations found between the contraceptive method at first intercourse and subsequent sexual behaviors are not fully understood.

Still, it has been hypothesized that contraceptive use adopted by women during early sexual experiences may become an integral part of their sex life and favor contraceptive use later in life.

A woman’s contraceptive choice at first intercourse might also be a marker of an underlying trait or risk-taking tendency.

Most women in the study first had intercourse between ages 15 and 19, a period when risk-taking tendencies can be high, due to biological, environmental, and cultural influences.

Unprotected sex without immediate adverse events may also empower women to believe they are not at high risk.

“This study highlights the importance of early sexual behaviors and may help understand patterns of women’s sexual behaviors,” the authors wrote.